A magnetic sector mass spectrometer of intermediate mass range and resolution is requested to meet the needs of a user group on the Homewood campus of the Johns Hopkins University from the Departments of Chemistry, Biology and Environmental Health Sciences. A range of projects of chemical and biological significance is described: (1) Biosynthetic studies of the aflatoxins, environmental mycotoxins, and of the classical and non-classical Beta-lactam antibiotics. (2) Asymmetric syntheses of enantiomerically pure synthons and natural products, new synthetic methdology for construction of carbocycles and modification of polycyclic aromatic hydrocarbons into electrophilic alkylating agents. (3) Characterizing synthetic glycoconjugates, including intermediates and degradation products, which will be used extensively in studies of receptor-mediated endocytosis of carbohydrates. (4) To identify alkylated amino acids from enzymes inhibited by the enzyme-activated-substrate approach and tracer studies of the mechanism of deamination reactions. (5) Investigations on the molecular basis of sunlight-stimulated melanogenesis and the interplay between this stimulation and the pathological condition of malignant melanoma.